Process for making tetrachlorodifluoroethane



Patented May 3, 1949 UNITED STATES PATENT OFFICE PROCESS FOR MAKINGTETRACHLORODI- FLUOROETHANE No Drawing. Application March 19, 1946,Serial No. 655,594

4 Claims. (Cl. 204-163) This invention relates to manufacture of tetra-The reaction effected may be represented by chlorodifiuoroethane, i. e.,1,1-difiuoro-1,2,2,2- the equation tetrachloroethane, CClsCFzCl (M. P.42 C., B. P. H F O] F 91.8" C.), a material which is especially usefulas Light I a solvent and as a chemical intermediate, and 5 H C F E; C1CT$ F which is substantially less toxic than the related H 01 1 alkylchlorides. The present improvements are Th reaction may b carried. outconvenient-1y directed particularly t0 production f by passing thestarting materials into and thru chlorodifluoroethane from ethylidenefluoride, a glass enclosed reaction pace subjected t th 2, a re d yavailable raw materialaction of light and heat. Provided proper tem- Amixture of ethylidene fluoride and sufiicient peratures are maintained,any form of light chlorine to effect complete substitution of all ofwhich efiects hemical reaction may be employed, e y o en atoms by chl ey e t d by such as infra-red rays, ultra violet rays, ordinaryextraneous heat to relatively high temperatures i d t l s, fluorescentlight, or high to efiect chlorination and formation of tetrawattagedrying lamps, Commercial lamps (e. g.

chlorodifluor ethane. ch a direct herm l 115 volt, 250 watt, initialmaximum beam candle chlorination operation in which chlorination ispower f about 16,000) having a spot reflector effected by hea alone.While not Ordinarily 0 and a high infra-red emission are practical sincejectionable in chlorination procedures in general, such equipmentfurnishes b th light and, heat, n e particular reactions to Which thisinVenand facilitates temperature control. While heat tion relatespossesses the marked commercial dismay be i d from th ame n r y as thelight, adva a e that t e outset of heating, 001114 necessary reactiontemperatures may be obtained peting reactions take place With the resultthat from extraneous h at, or fr m a combination of HF Splits out Of theethylidehe fluoride Further. extraneous heat and heat from the source ofaside from loss of the HF, it is not possible to get t,

ood yie ds o e desired product because of the The process is readilyadaptable to a continuvarious side reactions inherently efiected. ousOperation in which t ethyliden fluoride The principal Object of thisinvention is and chlorine are continuously introduced into a vis on ofone-step photochemical and thermal reaction zone, subjected therein tothe simultane processes to Which it is Possible to Prepare tetraousaction of actinic radiation and heat, and the chlorodifluoroethane athigh rates of production resulting reaction mixture continuously byexhaustive chlorination of ethylidene fluoride charged from t reactionZone to give good yields of tetrachlorodifluoroethane, Good conversion fethylidene fl id and,

but without so-called chlorinolysis (disunion of good yields oftetrachlorodifluoroethane depend carbon atoms by the action ofchlorine), without upon the ethylidene flu rid to chlorine m0] ratio,Substantial 1088 Of HF, and Without giving rise temperature of thereaction, light intensity, space to formation of excessive quantities ofundesired velocity per h (volumes of t t gas t by-p room temperature pervolume of reaction cham- In accordance with the invention; it has beenher per hour), and t ub tantial ab of found that the fore o Obj t y beaceomoxygen in the reaction mixture. The term conplished by subject n atu e of ethylidene version indicates the percentage by weight offluoride and chlorine to the Si lt O s action starting material whichreacts during the course of actinic radiation and heat at temperaturenot of th reaction, and the term yield denotes the less than 400 C. andnot more than 550 C., and percentage by weight of ethylidene fluorideinput recovering tetrachlorodifluoroethane from the which is recoveredas the desired end product.

resulting reaction product. i In usual operation, chlorine should be emf'ployed in quantities not less than 4 molecular proportions per mol ofethylidene fluoride. Lesser proportions of chlorine may be fed into thereaction chamber, but to no advantage since conversion of ethylidenefluoride would be corre- 5 spondingly reduced. An excess of chlorine ispreferable, and it has been found that relative to the amount ofchlorine employed, best results are obtained when there is introducedinto the reaction zone not less than about 4.5 molecular proportions ofchlorine per mol of ethylidene fluoride.

In accordancewith the invention, ,it has been, found that inorder tosatisfactorily carry :out they present one-step photochemical andthermal process and obtain substantial exhaustive chloria nation,temperatures in the reactor should be maintained not less than 400 C;and notmorethan 550 C. We find that in order to make-eh fective theconjunctive use;of-;.actinic radiation. 2

and heat and put the reaction on atone-step,v basis, temperatures inthe. reaction chamber: should be maintained at not less than 400 C.Temperatures of about 550 C. should not be exceeded in order to preventappreciable chlorinolr" 25,

ysis. As to temperature control it has been found that best conversionand yields are secured when temperatures in the reactor are held withinthe range-ht about1450+475fi 0,",

The reaction proceeds in the presence-of any; reasonable amount ofactinic radiatiom. although the speed of reaction appears to be fairlyproportional to the intensity ofili'ght, good results having beenobtainedrh when both light anduheat emanate from the same sourceot.electrical .energy, in .whichinstancelightintensityis high.

In the bettermodes of operation, space-velocity per hour should be notmorethan. 250,. and is preferably in the range,ofa75,-to 150. Oxygeninhibits the chlorination reaction and, in practice the process is,carried, out; under: conditions such, that the reaction. iseflected inthe presence ofless than 0.1 by weight, of oxygen .basedonthe; amount ofethylidene. fiuoridecharged.

The exit gas. of. the reactor contains HCl, some-chlorine,tetrachlorodifiuoroethane, smaller amounts of materials such astrichlorodifluoroethane, boiling .at.about -723 C., and trace.quantities; 10f other chlorinated derivatives 1-Of ethylidene=fi uoride.

To, recover the-- desired,1,ledifiuoro1,2,2,2-tetw rachloroethaneproduct, ,the; eflluent oil the reactor may be fed into a water scrubberin the .bot tom; ofwhich the tetrachlorodifiuoroethanez and usually;small, amountsof I not: so :highly chlorinated ethylidene,fluoridecollect as an oilor a so]- id :dependingrupon temperatureconditions in. the scrubber. The supernatant water dissolvessI-ICl,andcany excess. chlorine which may have been present passes thruuthe.waterrscrubb'ern After. separationc fromcthe waterrin e. the. scrubber;the collected mass may-be washed:with a mildacaustic solution toremoverlasttraces of HCl' and chlorine. The resulting 1. material may bedistilled under suitable conditionsto .recover' thetetrachlorodifluoroethane-inthe desired state of purity.

Alternatively, thereactor tail gasesmay be passed into areceiverexternally packed in icer Chlorinated reaction products condenseand 7 form a mushy semi lid-uid mass comprising-tet=rachlorodifluoroethane, andsmall amounts of not so highly chlorinatedethylidene fluoride. The gases exiting "the receiver may. be scrubbedwith water in which chlorinated" products stillcontained in the gasstream are collected partly as solids and partly as a heavy oil. Afterseparation of the mixture of heavy oil and suspended solids from thewater by decantation, such mixture may be combined with the mushysemi-liquid mass withdrawn from the receiver. The resulting combinedmass may be then washed with dilute alkali to remove chlorine andacidity, and the washed mass distilled under conditions suitable torecover tetrachlorodifluoroethane.

Following is an example of practice of the invention. The all glassreactor used consisted of a 22.5..cm..length.of,2.5cm..O,D..glass.,tubing opening,intota,l5t75icm.. O. D. glass tube;35icm. long. Provision was made for introducing the reactants at the tipof the smaller tube and for drawing of? reaction products at the otherend of the apparatus. A= glass-thermocouple well was fitted into the'reactor in order to keep check on internal ,temperatures. Lightzandheat were provided by threeu-ll5uvolt 250-watt drying lamps arranged todistributealightzandi heat approximately equally over the entirereaction zone. Heat losses were prevented. by, wrapping the entireapparatus in aluminum foil. Amixture of 79 parts by Weight of ethylidenefluoride and 602 parts of chlorine (representing a molar ratio of 125.2)was passed through the reactor during an 80 minute period. p -ve iylperihour:wasiflOtandthetemperature=was=maintained .at 455*4757'0;Theareeactor tail gases were .passed.intoramexternally ice;packedureceiver; and c2115.zpartseoficreaction:proda not were:collected; which product: comprised.;tet-;- rachlorodifiuoroethane andsom'ertrichlorodifluoa roethane. Occluded I-lCl an-dixchlorine. wererreemoved by, atli'ghtacaustic wash; Upon distillae tion,..there\:were+recovered aswstill, residue 197.: parts of.tetrachlorodifiuoroethanerboiling .inthe rangeiof 92 C. Yieldzwas;8l%.

We-claim':

1; The-process for, preparing: :tetracl'llorodifluoa roethane whichcomprisessubjecting aniixture of: ethylidene :fluoride and notsubstantially less; than 4 :molecular proportions 10f chlorine :to the:simultaneous action. or actinic radiation and iheat? at -1atemperaturerofa'not lessathan; 400? C. and: not:mcre .-than;550?' O. fora period of timex'suffi cient to .efiect, formation, of substantial:xyieldr of tetrachlorodifiuoroethane and recovering 3 tetra-i.chlor-odifluoroethanewfrom qthe :resultingareactionw products.

2. The, process fOly preparingytetrachlorodiflu: oroethan'e which;comprises subjecting a mixture: ofethylidene, fluoride and mot:substantially less. than 4 molecularrproportionsvoflchlorine torthe:simultaneous zaction 10f: actinici radiation: and heat ata temperature-inwthei range of 2 about 450475? C. fon-a-period oftime-suflicientxto:effect' formae tion y of; substantial yield; oftetrach-1orodifluoroethane, andrecovering tetrachlorodifiuoroethane from.thEvIGSIlltlIlgglGfiClllOIl products.

3. The process form preparing :tetrachloro'difim orpethane :whichucomprises 1-, continuously; intro, ducing, into a areaction;zoneethylidene fluoride and a not substantially ,vless -.,than-,.4moleculaiw pro portions of chlorine, subjecting the mlXfitlI'ExOf Iethylidene fluoride. and chlorine in ,-sai d .zone-.-to thersimnltaneousaction ofdactinic .radiationxandn heat=at avtemperature oi notless than490? C. and v not. more. than, 550? 0., ,passi-ngg, said; mixturesthroughmsaidtzone atra, rate. such; $31170; maintain. said .ethylidene.fluorideandphlorine: in isaicliezone for. a period'of.time,.suflicientrto,.efiect formation of substantial yield 'oftetrachlorodifluoroethane,. continuously discharging the resultingreaction products from said zone, and recoveringtetrachlorodifluoroethane from said reaction products.

4. The process for preparing tetrachlorodifluoroethane which comprisescontinuously introducing into a reaction zone ethylidene fluoride andnot substantially less than 4.5 molecular proportions of chlorine,passing said ethylidene fluoride and said chlorine through said zone atspace velocity in the range of 75-250 per hour while subjecting themixture of ethylidene fluoride and chlorine in said zone to thesimultaneous action of actinic radiation and heat at temperature in therange of about 450-475 C., continuously discharging the resultingreaction products from said zone, and recoveringtetrachlorodifluoroethane from said reaction products.

JOHN D. CALFEE.

PATRICK A. FLORIO.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,004,072 Hass et al June 4, 19352,407,246 Benning et a1 Sept. 10, 1946 OTHER REFERENCES

